Electromotive devices are known for use both in transforming electrical energy into mechanical power and transforming mechanical power into electrical energy. In both cases, the energy or power-producing capability results due to relative movement between a magnetic field and electrically conductive elements.
Light weight motor, alternator and generator devices are well known and some are capable of operation at high speeds. However, many such devices are not capable of producing high power at high speeds. For example, high power density devices of 0.6 horsepower per pound of weight are known for intermittent operation, but such devices are incapable of continuous operation at high power densities in excess of 1.0 horsepower per pound.
Prior electromotive devices have not been capable of simultaneous high speed and high torque operations, nor have they provided efficiency of operation.
Known electromotive devices which include a stator and rotor arrangement can include magnetic elements on the rotor (for example, see U.S. Pat. Nos. 3,663,850; 3,858,071; or 4,451,749) or on the stator (U.S. Pat. Nos. 3,102,964; 3,312,846; 3,602,749; 3,729,642 or 4,114,057). Further more, double sets of polar pieces can be utilized, as in U.S. Pat. No. 4,517,484.
In addition, a shell rotor has been suggested in U.S. Pat. Nos. 295,368; 3,845,338 and 4,398,167, with a double shell rotor arrangement suggested in U.S. Pat. No. 3,134,037.
Bundles of wires have been used in place of a single conductor in the armature assemblies of motors for high voltage and high current usage and/or to reduce current flow loss due to skin effect, and heating due to eddy currents, see U.S. Pat. Nos. 497,001; 1,227,185; 3,014,139; 3,128,402; 3,538,364 or 4,321,494, or British Patent No. 9,557. The plural wires are used with solid or laminated cores, see U.S. Pat. No. 3,014,139 or 3,128,402; or British Patent No. 9,557.
Some prior electromotive deVices, such as U.S. Pat. No. 3,275,863, have a power-to-weight ratio of up to one horsepower per pound and U.S. Pat. No. 4,128,364 teaches using a gas, liquid, or a mixture thereof to cool a motor to increase its power handling capability.
Many of the preceding difficulties in achieving a high power-to-weight ratio electromotive device have been addressed by a dispersed conductor electromagnetic device which is the subject of a co-pending U.S. patent application by the inventor of the present invention titled "Lightweight High Power Electromagnetic Transducer". The co-pending design utilizes a straight-sided armature bar of powdered iron which allows full exposure of the copper to the magnetic field. In addition, the powdered iron does not have the flux-carrying ability that the silicon iron does. To minimize the eddy current effect, it utilizes extremely fine wire.. The armature bars are fabricated from powdered iron to further insure the 3-d dispersion necessary to reduce/minimize back electro-motive-force (back EMF).
Unfortunately, this approach is inefficient in terms of power-in versus power-out due to the resistance characteristic of fine wire. This characteristic causes significant energy loss in the form of heat at higher operating levels, which translates into lost power and efficiency. In addition, the straight bars do not lend themselves to standard production automatic winding techniques as the coils would slip outward from between the bars.
The power loss due to fine wire resistance is compensated for by increasing the amount of permanent magnet material beyond the saturation level of the iron bars. Aside from the costs of additional material, the bulk of this additional flux goes into the copper in the form of eddy current loss and is dispersed, leaving very little gain in power for the additional material investment. While the preceding and other various arrangements have been used to attempt to achieve a high power-to-weight ratio electromotive device, they have not been completely successful. In particular, the prior art does not teach the necessity to disperse the conductors to enable high speed operation. This is due, at least in part, to a widely accepted theory that the magnetic field is relatively small in the non-magnetic winding conductors. With conductors built according to conventional teachings, it has been found that torque, at constant current, decreases with increasing speed. This result is contrary to the conventional expectation that torque will remain high as speed increases.